Interacting in-plane molecular dipoles in a zig-zag chain

TL;DR

This paper theoretically investigates a one-dimensional zig-zag chain of in-plane polarized dipoles, revealing diverse quantum phases and phase transitions controlled by polarization angle and interaction strength, including BKT and dimerized phases.

Contribution

It introduces a comprehensive phase diagram for polarized dipoles in a zig-zag chain, connecting the geometry and polarization to quantum phase transitions and effective models.

Findings

Small chain angles lead to BKT-type transitions.

Large chain angles induce a gapped dimerized phase.

System behavior is tunable via polarization angle and interaction strength.

Abstract

The system with externally polarized dipole molecules at half-filling moving along a one-dimensional zig-zag chain is studied theoretically, including the ground-state phase diagram. The dipoles are oriented in-plane. Together with the geometry of the chain this gives rise to a bond-alternating nearest neighbor interaction due to simultaneous attractive and repulsive interactions. Because of the quantum Zeno effect due to the reactive nature of molecules the system can be treated as hard-core. By tuning the ratio between the nearest-neighbor interaction and hopping, various phases can be accessed by controlling the polarization angle. In the ultra-strong coupling limit, the system simplifies to a frustrated extended axial Ising model. For the small coupling limit, qualitative discussion of the ordering behavior using effective field theory arguments is provided. We show that when chain angle is small, the system mostly exhibits BKT-type phase transitions, whereas large chain angle would drive the system into a gapped (Ising) dimerized phase, where the hopping strength is closely related to the orientation of dimerized pairs.